The San Francisco company has raised about $100 million in the last eight months, Nextdoor Chief Executive Nirav Tolia said.

A person familiar with the funding pegged the valuation at north of $500 million.

Nextdoor is like Facebook but for a neighborhood: a private network to find a baby sitter, borrow a cup of sugar, organize a block party or spread word of a break-in.

It's not the first start-up to try to network neighbors, but it's the first to gain momentum.

It launched two years ago. Now more than 22,500 neighborhoods in the U.S. use Nextdoor, 1 in 7 neighborhoods across the country, the company said.

Kleiner Perkins partner John Doerr said he's wagering NextDoor will become the go-to social network for neighborhoods, the way LinkedIn has become the de facto network for working relationships and Facebook has become for friends.

"It's the neighborhood water cooler," Doerr said. "I think there is a big, big market opportunity for a company that is a social network for our local lives."

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It's another significant vote of confidence for Nextdoor. Doerr is arguably the most successful venture capitalist that Silicon Valley has ever seen.

Doerr has been playing catch up on social networking. He bought into Facebook at a $52 billion valuation and Twitter at a $3.7 billion valuation, and has been making some major investments in companies that combine social, local and mobile, a trend which he dubbed "SoLoMo." He coined the term in 2010.

"I have long believed that there are just monster market opportunities around local services, local commerce and local use of these technologies," Doerr said.

NextDoor is also picking up another influential investor in Lee Fixel from Tiger Global, who has quietly invested in Facebook, LinkedIn, Square, SurveyMonkey and other prominent Silicon Valley companies.

Tolia said the new investors bring valuable expertise to help the company expand its reach, particularly internationally.

"We are going to step on the gas a little," he said.

He added that Nextdoor still has $90 million in the bank, which "gives us so much freedom to do right thing."